光纤光栅耦合附加腔被动锁模激光器特性的分析

对光纤光栅耦合附加腔被动锁模激光器进行了详细分析 ,得到了附加腔锁模激光器的振荡条件。研究表明在稳定工作状态下 ,附加腔锁模激光器的增益、损耗、两腔之间的耦合效率以及激光振荡波长等参数在复平面上将构成一个近似的等腰三角形。对振荡初期增益的研究表明 ,主腔增益在光纤光栅中心波长两侧有明显的不对称性 ,这将会造成激光器输出光脉冲光谱的不对称性。对谐振腔的进一步分析表明 ,由于光波在光纤光栅中具有一定的穿透深度 ,为了实现激光振荡 ,两谐振腔的名义长度差需要保持一个确定的值     

The frequency chirp of current modulated semiconductor diode lasers

Wavelength modulation or frequency chirp accompanies the power modulation of current modulated semiconductor diode lasers. Standard diode laser theory predicts that the laser gain and wavelength are clamped for modulation frequencies well below the relaxation oscillation frequency (except at frequencies so low that temperature modulation in the laser induces wavelength modulation). The wavelength clamping is not observed in experiments. We show that straightforward analysis of the wave equation for the laser waveguide can re-solve this discrepancy.     

1.5-μm wavelength tunable phase-shift-controlled distributedfeedback laser

A 1.5 μm wavelength tunable phase-shift-controlled distributed feedback laser diode is studied. This wavelength tunable laser controls the light output power and the oscillation wavelength independently by current injection. During wavelength tuning, the submode suppression ratio is large and an almost constant spectral linewidth from 24 to 29 MHz is achieved over a wavelength tuning range as wide as 113 GHz (9.0 Å). The threshold gain change and the loss change are small during wavelength tuning and as a result an almost constant light output power is achieved     

Gain spectrum equalization of all-optical gain-clamped erbium-dopedfiber amplifier

We experimentally investigate the gain spectrum of erbium-doped fiber amplifiers whose gain is clamped by internal laser oscillation. The gain is ideally clamped and immune to the input signal power in the wavelength range of 17 nm. The clamped gain spectrum is equalized by a Mach-Zehnder interferometer, and we achieve the 17-nm-wide uniform gain, which is not dependent on input optical power levels     

半导体光纤环形腔激光器调谐特性的实验研究

采用国产半导体器件,组建了半导体光纤环形腔激光器(FRSLs)的实验装置及相应的测试系统,系统地研究了FRSLs的输出和调谐特性.结果表明,已实现高速调制情况下的动态单纵模调谐,并获得波长调谐范围大于36nm的稳定光脉冲输出.确立了FRSLs的阈值特性、输出功率等物理参量与振荡波长之间的关系,提出通过控制分光比来优化和兼顾FRSLs的调谐范围及输出功率.实验结果较好地与理论模拟结果相吻合,为进一步改善FRSLs的性能指标提供了实验依据.同时,这些分析与结论对于相关结构类型的激光器设计也具有一定的参考价值.     

增益与光强的相关系数对光栅外腔半导体激光器稳态特性的影响

本文引入增益与光强的相关系数h,建立了光栅外腔半导体激光器的稳态模型。数值计算结果表明:激光器的其它参数必须与h相匹配,才能使激光输出的稳定区增大,且可在一定波长范围内进行选频,保证很好的单模性。     

Broad-band wavelength-tunable, single frequency, and single polarization bismuth oxide-based erbium-doped fiber laser

We demonstrate a broad-band wavelength-tunable Bismuth Oxide-based Erbium-doped fiber (Bi-EDF) laser covering both the conventional wavelength band and the long wavelength band. It features single frequency and single polarization oscillation; the former is obtained by making the cavity length short and incorporating an intracavity narrow-band fiber Fabry-Pe/spl acute/rot filter, and the latter is achieved with a sigma laser configuration using nonpolarization maintaining fibers. Tuning over 90 nm (1520-1610 nm) is achieved by utilizing the broad gain bandwidth of Bi-EDF amplifier.     

掺镱光纤激光器的多波长振荡特性

利用Sagnac梳状滤波器,研究了环形腔掺镱光纤激光器(YDFL)在室温和77 K时的多波长振荡行为。结果表明,在室温和77 K时,掺镱光纤(YDF)均呈现明显的非均匀加宽效应,使得掺镱光纤激光器的起振波长数随抽运光功率的提高而增多。但在室温下,因均匀加宽效应强,掺镱光纤增益的非均匀加宽并不能补偿其内禀不平坦的增益谱,造成波长缺失现象,且当波长间隔减小至0.8 nm时,均匀加宽效应引起的波长竞争造成了多波长振荡的稳定性下降。而在77 K时,掺镱光纤非均匀加宽效应明显增强,在0.8 nm的波长间隔下,无波长缺失现象,将起振波长数增加到32个,且多波长振荡稳定。     

Broadband tuning (170 nm) of InGaAs quantum well lasers

The wavelength tuning properties of strained InGaAs quantum well lasers using an external grating for feedback is reported. Tunable laser oscillation has been observed over a range of 170 nm, between 840 and 1010 nm, under pulsed current excitation. The optimal conditions for broadband tunability for the InGaAs lasers are different from GaAs lasers, which is attributed to a difference in spectral gain curves. Together with an optimised GaAs quantum well laser the entire region between 740 and 1010 nm is spanned.<>     

Locking characteristics of a side-mode injected semiconductor laser

This paper is focused on an experimental study of the injection-locking bandwidth and the relaxation oscillation frequency in a side-mode injection-locked semiconductor laser. It is shown that, for such a laser, the injection-locking bandwidth and the relaxation oscillation frequency are related to the injection power and the wavelength of the target injection mode. At fixed launched injection power, the injection-locking bandwidth and relaxation oscillation frequency can be increased when the injection wavelength is detuned to the short-wavelength side of the free-running wavelength, while the relaxation oscillation frequency decreases when the injection wavelength is set to the long-wavelength side of the free-running wavelength. The results are in good agreement with theoretical predictions     

Theory of the synchronously pumped fiber Raman laser

Analyses of the synchronously pumped fiber Raman laser are presented under the parabolic approximation for gain shaping in both frequency and time domains. A master equation for the Stokes pulse consists of the group velocity dispersion of the fiber, the gain dispersion of the stimulated Raman scattering, a gain-shaping term due to the pump curvature, small depletion, and a walk-off effect. The pump power dependences of the Stokes power and the pulse width and the threshold condition are revealed. The frequency tunability of the present laser is also discussed. It is shown that the oscillation wavelength (carrier frequency of the Stokes pulse) will change linearly with Stokes power because of walk off during depletion.     

Effect of Optical Delay on the Suppression of the Power Transient Excursion in a Combined Gain‐Controlled Erbium‐Doped Fiber Amplifier

This report describes the effect of optical delay on the suppression of the power transient excursion in a combined gain‐controlled erbium‐doped fiber amplifier with an internal optical feedback loop (OFL). A simple homogeneous model showed that the optical delay caused a phase change in the oscillation of the surviving and laser channels, which resulted in a reduction of the overall power transient excursion. In addition to the reduction, a real system with a 1528.7‐nm OFL shifted the oscillation upward or downward according to channel removal or addition, whereas another one with a 1560.9‐nm OFL did not. This different transient behavior reflected a control‐wavelength dependence on optical automatic gain control, where spectral‐hole burning dominated over relaxation oscillation for 1528.7 nm, and vice versa for 1560.9 nm.     

采用可调Mach-Zehnder滤波的波长可切换掺铒光纤激光器

为了实现高稳定性的可调谐激光输出,提出并设计了一种基于马赫-曾德（M-Z）结构和光纤光栅串结合的掺铒光纤激光器,在M-Z干涉结构的一个干涉臂中加入光学延迟线（ODL）,实现对干涉间隔的灵活可调。系统结构设计采用976 nm波长的LD作为泵浦源,长度为6 m的掺铒光纤作为增益介质;采用光栅串将特定波长的光反射回环形腔形成振荡;采用M-Z结构产生梳状滤波用来对光栅串反射回的光进行选择;通过调节ODL来改变腔内损耗,进而实现激光的可调谐输出,并通过在系统中加入可饱和吸收体（SA）和子腔结构来抑制波长的跳变。实验中,在泵浦功率为100 mW时,实现了单波长双波长和三波长的稳定的激光输出。单波长共输出13个,调谐范围为1 570~1 596 nm,调谐间隔为2 nm,边模抑制比均大于50 dB。     

The POPOP dye vapor laser

We report a comprehensive study of the operation of a laser using the organic scintillator dye POPOP in the vapor phase. Laser operating parameters have been determined, and we describe tuning experiments which demonstrate an oscillation range of 25 nm. Gain measurements as a function of wavelength and time are reported for transverse pumping with the 337.1-nm output of a pulsed N2laser. The quantum efficiency has been measured as a function of temperature and pump wavelength, and a preliminary study has been made of the effect of buffer gases on the quantum efficiency and the gain. Spectral condensation measurements show 90 percent of the broad-band laser output can be obtained in a 1-nm band-indicating that even in a dilute vapor, the thermalization time of the laser levels isgg1ns. We conclude by discussing the implications of these results for the achievement of an electrically pumped dye vapor laser.     

Visible and ultraviolet radiation generation using a gas-loaded free-electron laser

Gas loading of a free-electron laser modifies the phase-matching condition while the small-signal gain expression remains the same when written in appropriate form. This permits a wider parameter space than the vacuum FEL, which is particularly advantageous at shorter wavelength operation. Scattering of the electrons by the gas limits the interaction length, but available gains are still high enough to allow oscillation build-up. For example, a 0.5-μm wavelength helical wiggler FEL utilizing a 41 MeV electron beam is restricted to a length of 14 cm, has a small signal gain of 21 percent, and builds up to saturation in less than 1μs. Tunability of this device over several microns is easily obtained by changing the gas pressure.     

连续激光泵浦重水气体分子产生THz激光辐射的阈值分析

利用连续运转二氧化碳激光器的9R(22) 输出谱线泵浦重水气体(D2O)分子可以产生波长为385微米,频率为0.78THz的连续激光辐射输出,采用半经典理论分析方法并结合三能级系统模型可以对此激光过程进行有效的分析,通过合理的近似简化了求解过程,得到了光场中太赫兹激光信号增益系数Gs和泵浦光信号吸收系数Gp的解析表达式,通过对求解结果的分析,计算出产生THz激光振荡的泵浦阈值条件为6.24×10-3W/mm2,一般情况下,在泵浦激光输出光斑面积为0.25mm2时,要求泵浦激光谱线的输出功率达到1.6mW以上才能形成THz激光辐射。     

Experimental and theoretical analysis of relaxation-oscillationsand spectral hole burning effects in all-optical gain-clamped EDFA's forWDM networks

Experimental and theoretical analysis of the gain dynamics of all-optically stabilized multichannel erbium-doped fiber amplifier (EDFA) and the impact on wavelength division multiplexed (WDM) networks performance requirements is presented. In particular, we focus on precise analysis of the detailed transient response of the surviving channel and the relaxation oscillations of the compensating (lasing) signal. The main objective of this work is to experimentally and theoretically analyze and examine some of the critical factors such as, lasing wavelength, gain recovery time, relaxation oscillation frequency of the feedback loop, and the number of channels dropped/added, that affect the transient power excursions in the surviving channel. First, we consider the applicability of laser automatic gain control (AGC) to control fast power transients in WDM optical networks and reports the first high resolution measurements of transients in such gain controlled EDFAs. Second, the experimental results are compared with those predicted from a numerical simulation of the dynamic of the gain controlled EDFA     

工作在L波段的多波长Er3 /Yb3 共掺光纤激光器

采用Er^3 ／Yb^3 共掺双包层光纤(EYDF)作为增益介质，利用一段标准的多模光纤作为空间梳状滤波器，于室温下实现了5个波长的稳定输出。通过调节偏振控制器的状态，可以实现对波长振荡个数和波长间隔的控制。腔中不加任何的稳定装置，在激光输出功率高于207mw时，仍能够得到多波长的稳定振荡，单一波长的线宽窄于0．15nm，边模抑制比大于32dB。通过优化单模光纤与多模光纤的熔接，选择更加合适的多模光纤，可实现更多波长个数的稳定的多波长输出。     

脉冲空心阴极放电中Kr Ⅱ 469.5nm激光振荡的增益特性研究

采用作者提出的“自身光信号放大法”,利用放电管中本身的激光振荡信号,测试了脉冲空心阴极放电中KrⅡ469.5nm激光振荡的增益的时间与空间特性。测试结果表明,激光振荡首先从空心阴极管中心产生,然后扩展到整个管。在最佳He-Kr充气比时,最大增益可达103%m-1,这是在放电后约2μs时达到,这和激光脉冲中的峰值相对应。就现有报道中,就这条谱线的激光振荡而言,所达到的增益是最高的。用标定损耗片插入法测定了同样的放电条件下的增益,验证了上述测试结果的可靠性。     

External-cavity semiconductor laser with focusing grating mirror

A novel external-cavity semiconductor laser with a focusing grating mirror (FGM), which enables a single-mode oscillation at a specified wavelength, is proposed. The optical properties of the FGM, which is a computer-generated holographic grating with chirp and bend structure, are numerically analyzed. An optimally designed FGM for realizing laser oscillation at a specific wavelength of 1.30 μm is fabricated by using a computer-controlled electron-beam writing system. The fabricated FGM with grating area of 1×1 mm² is combined as an external feedback mirror with an InGaAsP-InP semiconductor laser of 1.3 μm wavelength range, and the lasing characteristics are experimentally measured. Stable and single-mode oscillations with spectral line width less than 10 MHz are observed